Point defects in beryllium-doped GaN

Detailed analysis of the defect-related photoluminescence (PL) in semi-insulating and $n$-type Be-doped GaN samples grown by molecular beam epitaxy is presented. The dominant PL bands in these samples are the ultraviolet $\left({\mathrm{UVL}}_{\mathrm{Be}}\right)$, yellow $\left({\mathrm{YL}}_{\mathrm{Be}}\right)$, red $\left({\mathrm{RL}}_{\mathrm{Be}}\right)$, and green (GL2) bands. The ${\mathrm{UVL}}_{\mathrm{Be}}$ band is caused by electron transitions via the $0/-$ level of the ${\mathrm{Be}}_{\mathrm{Ga}}$ acceptor located at 113 meV above the valence band. The ${\mathrm{UVL}}_{\mathrm{Be}}$ band is quenched above 60 K, and the quenching is tunable by excitation intensity. The quenching of the ${\mathrm{YL}}_{\mathrm{Be}}$ above 200 K is likely related to an acceptor level at 0.3 eV. In semi-insulating samples, the quenching temperature is tunable with the intensity of the excitation laser. Based on the first-principles calculations, the ${\mathrm{YL}}_{\mathrm{Be}}$ band is preliminarily attributed to the ${\mathrm{Be}}_{\mathrm{Ga}}\text{−}{\mathrm{V}}_{\mathrm{N}}\text{−}{\mathrm{Be}}_{\mathrm{Ga}}$ complex. The new ${\mathrm{RL}}_{\mathrm{Be}}$ band is attributed to the internal transition in the ${\mathrm{Be}}_{\mathrm{Ga}}\text{−}{\mathrm{V}}_{\mathrm{N}}$ complex with a deep $+/0$ transition level at about 0.95 eV.